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8x8 RGB LED matrix — Parallax Forums

8x8 RGB LED matrix

RaymanRayman Posts: 14,826
edited 2012-09-12 16:52 in Propeller 1
Ok, so I don't really have any spare time at all...·

But, I've been looking at this 8x8 RGB LED matrix from Sparkfun.

They sell a lame controller board for it that I'm convinced would be much better if
driven by a Propeller [noparse]:)[/noparse].·· They only get 256 colors, but I think I can get 24-bit
color using a Prop and three dual 2:4 demultiplexers in ACT logic...

This is the lowest cost source I've found.

Should be no trouble to make this extensible to arbitrary large displays.
But, I'm thinking that a 32x32 matrix would be pretty cool....


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My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm

Comments

  • mparkmpark Posts: 1,305
    edited 2009-10-31 07:10
    Ray, have you seen this thread in the sandbox?
    http://forums.parallax.com/showthread.php?p=846433

    8x8 RGB, $14.50 each if you order 10.
  • bisonburtbisonburt Posts: 2
    edited 2009-10-31 15:13
    FYI: I wired up a PCB using sparkfun's 8x8 rgb display using the propeller. I used the the same driver circuitry (595's and a darlington driver) and was able to pump out some spin code in no time for basic operation to turn on each led and cycle through the display fast sufficiently to not cause any flicker.

    With a little more work and perhaps some assembly you could get the display to show more colors.
  • RaymanRayman Posts: 14,826
    edited 2009-10-31 16:58
    This thing almost plugs directly into the Propeller Platform. Just a few mm off... Still might go if we bend the pins a little.
    That would have to be the easiest way to start playing with it.

    You can use all the Prop pins if you're just doing one 8x8 panel.
    I've seen others connect directly to LEDs (with no resistors). Presumably by using PWM to keep the average current down and counting on some max. current out of a Prop pin.

    I'm a little worried that 3.3 V isn't enough to forward bias the blue LEDs though...

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    My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm
  • bisonburtbisonburt Posts: 2
    edited 2009-11-01 01:17
    I had to run 5 volts to the 595's get the blue LED's to work. Image attached - sorry for the over saturated color - It was the best I could do for now.
    led.jpg
    294 x 500 - 24K
    led.jpg 23.8K
  • RaymanRayman Posts: 14,826
    edited 2009-11-01 12:18
    Thanks for that info. Ok, the common anode messes up my earlier idea... But, maybe use 24 pins for the cathodes and put a 1:8 demux in ACT logic on the anode side...

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    My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm
  • RaymanRayman Posts: 14,826
    edited 2009-11-01 17:52
    Seems that some of these devices are common anode and others are common cathode...

    The 100 mA limit on every group of 8 pins Prop is a real problem...

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    My Prop Info&Apps: ·http://www.rayslogic.com/propeller/propeller.htm
  • IntentssIntentss Posts: 1
    edited 2012-09-12 16:39
    Just FYI re-sellers are making a killing on these things: the 8x8 RGB matrix can be bought from china for about 2.3usd each for orders over about 10. You will pay about $50 in shipping. Check http://www.alibaba.com/
  • RaymanRayman Posts: 14,826
    edited 2012-09-12 16:52
    Might have to lower the price on PropRGB then...
    http://www.rayslogic.com/Propeller/Products/PropRGB/PropRGB.htm

    Still, I would worry about the quality of cheaper ones. Guess it depends on what you want it for...

    I have a feeling that cheeper ones will not be very bright and don't produce "white" when R,G,&B are all fed the same current...
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